The present invention relates to a method of processing a substrate.
A semiconductor-device manufacturing process includes a film-forming step of forming an inter-layer insulating film, such as, a SOD (Spin On Dielectric) film on a semiconductor wafer. Such a film-forming step requires a coating step of applying a coating solution on the wafer.
In the coating step, a nozzle is moved over the wafer center and a specific amount of coating solution is sprayed from the nozzle onto the wafer center, followed by rotating the wafer so that the coating solution is spread over the wafer surface by centrifugal force, thus a coating film being formed on the wafer surface at a specific thickness.
The coating solution adheres to the tip of the nozzle after completion of spraying. The adhered solution will be dried and crystallized if not removed, causing generation of particles. It is thus required to remove, as much as possible, the coating solution adhered at the tip of the nozzle after completion of spraying.
Not only that, the top surface of the coating solution will stop in the nozzle near the tip thereof when spraying halts. The coating solution remaining in the nozzle will also be dried and deteriorated. The coating solution remaining in the nozzle thus requires to be protected from being dried and deteriorated for the next use.
To solve problems, for example Japanese Unexamined Patent Publication No. 4-200768 discloses a method of soaking a nozzle into a bath of solvent after completion of spraying.
Such a method is, however, disadvantageous in that the nozzle inner surface will not be washed well because the nozzle will not be filled enough with solvent completion of spraying.
The coating solution remaining in the nozzle will be protected from becoming dry when the nozzle is soaked into the bath. The remaining solution will, however, touch the solvent and hence could be mixed with the solvent, which could cause contamination and deterioration of the coating solution, thus resulting in incomplete formation a coating film on a wafer to be processed next.
Moreover, much dummy dispensing after the completion of the coating step for one wafer in order to supply a pure coating solution to the next wafer causes increase in consumption of coating solution and hence high cost.